Stabilisation and altitude tracking of a four-rotor microhelicopter using the lifting operators

Abstract

The lifting methodology can be used for simplifying the closed-loop stability study of a system in which the measurement data are acquired at different frequencies. This is because the lifting operators allow treating this kind of systems as if there is only one control frequency, which reduces the complexity of the problem in a very important way. The four-rotor microhelicopter designed by the authors, whose control is faced, is a nonlinear plant with sensors operating at two different frequencies. First, the system is linearised cancelling the rotors dynamics. Then, the authors implement a model reference adaptive control structure for identifying the gains of the linear reference plant and performing the adaptive control of the microhelicopter. At this point, the system stability study is carried out by just computing the eigenvalues of the closed-loop states matrix thanks to the lifting operators.